Methods and Techniques of Irrigation

8/11/2019 Methods and Techniques of Irrigation

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of system

Drip

sprinkler

sprinkler

Moving

sprinkler

other sprinkler

irrigation supply)

irrigation supply)

Methods and techniques of Irrigation

in Australia:

WhyDrip

Environmental Sustainability:

Efficiencies for irrigation application systems

Watersaving (ie. greaterefficiency and reducedlosses)

Reduceddrainage hazards

Ability to utilise lower quality water

Reducedfarm inputs

Increased land utilisation (ie. irregular topography)

Less off-site impact of nutrients

Crop & Farm Benefits

Cost savings (ie. energy,water,fertilizer)

Increased distribution uniformity

Precision water application

Increased productionper ML

Improved planthealth (ie. salinity,fungal, nutrientmanagement)

Increased access/traffic ability Greaterweed control

SDI Distribution Uniformity (DU) can be93% or higher,compared with sprinklers at 60% to 80%and surface irrigation at50% to 60%

Source:SouthAfrican Irrigation Institute,2005

Drip Types

There are two typesof drip irrigation:

Surface drip irrigation: Wateris applied

directly to the soil surface; and

Sub-surface drip irrigation (SDI): Wateris

applied below the soil surface

The type of drip system used should be

determined with careful consideration given tocrop type,soil type and condition, climate andthe goal desired from installing a drip system.

Surface Drip Irrigation Sub-surface Drip Irrigation


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Irrigation technology used on Australian farms

Farmers use a variety of irrigation techniques to apply water to their crops and pastures:

Drip or trickle and sprinkler systems (i.e. micro sprinklers, travelling guns, booms, center-pivots, lateral-

moves and solid set systems) were common. Drip irrigation was the most common method of irrigation

in Australia during 200809, when 11 401 (22.6%) of agricultural businesses used this method. Surface

irrigation methods, such as border check and furrow, were the second most common, used by 16.5% of

irrigating agricultural businesses during 200809.

Types of irrigation systems:

Furrow systems

This system comprises a series of small, shallow channels used to guide water down a slope across a

paddock. Furrows are generally straight but may also be curved to follow the contour of the land,

especially on steeply sloping land. Row crops are typically grown on the ridge or bed between the

furrows, spaced from 1 m apart.

Flood or border check systems

These systems divide the paddock into bays separated by parallel ridges/border checks. Water flows

down the paddock's slope as a sheet guided by ridges. On steeply sloping lands, ridges are more closely

spaced and may be curved to follow the contour of the land. Border systems are suited to orchards and

vineyards, and for pastures and grain crops.

Level basin systems

These systems differ from traditional border check or flood systems in that the slope of the land is level

and the area's ends are closed. Water is applied at high volumes to achieve an even, rapid ponding of

the desired application depth within basins.

Centre-pivot sprinkler systems

A centre-pivot sprinkler is a self-propelled system in which a single pipeline supported by a row of

mobile towers is suspended 24 m above ground. Water is pumped into the central pipe and as the

towers rotate slowly around the pivot point, a large circular area is irrigated. Sprinkler nozzles mounted

on or suspended from the pipeline distribute water under pressure as the pipeline rotates. The nozzles

are graduated small to large so that the faster moving outer circle receives the same amount of water asthe slower moving inner circle.


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Hand move sprinkler systems

Hand move sprinkler systems are a series of lightweight pipeline sections that are moved manually for

successive irrigations. Lateral pipelines are connected to a mainline, which may be portable or buried.

Hand move systems are often used for small, irregular areas. Hand move systems are not suited to tall-

growing field crops due to difficulty in repositioning laterals. Labor requirements are higher than for allother sprinklers.

Solid set/fixed sprinkler systems

Solid set/fixed refer to a stationary sprinkler system. Water-supply pipelines are generally fixed (usually

below the soil surface) and sprinkler nozzles are elevated above the surface. Solid-set systems are

commonly used in orchards and vineyards for frost protection and crop cooling. Solid-set systems are

also widely used on turf and in landscaping.

Travelling gun sprinkler systems

Travelling gun systems use a large sprinkler mounted on a wheel or trailer, fed by a flexible rubber hose.

The sprinkler is self-propelled while applying water, travelling in a lane guided by a cable. The system

requires high operating pressures, with 100 psi not uncommon.

Side-roll wheel-move systems

Side-roll wheel-move systems have large-diameter wheels mounted on a pipeline, enabling the line to

be rolled as a unit to successive positions across the field. Crop type is an important consideration for

this system because the pipeline is roughly 1 m above ground.

Linear or lateral-move systems

Linear or lateral-move systems are similar to centre-pivot systems, except that the lateral line and

towers move in a continuous straight path across a rectangular field. Water may be supplied by a

flexible hose or pressurized from a concrete-lined ditch along the field's edge.


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Comparing the efficiency of irrigation systems Australia

System design and management can have a big effect on application efficiency. For example, a flood

irrigation system using border check irrigation design, a sprinkler irrigation system using centre-pivot or

linear move and a drip system can have the same level of application efficiency (Figure 1) depending on

the system design and level of management. This has been demonstrated in farm trials in Victoria,where all components of the water balance were measured for flood and centre-pivot systems; both

systems had an application efficiency of around 82% (Wood et al. 2007). This means that conversion

from a flood irrigation system to a pressurized system may not deliver the expected increase in

application efficiency if management is poor. However, as the percentile bands for sprinkler and drip

systems are higher than for flood systems, the benefit of greater financial investment in a pressurized

system is that it will be much less susceptible to water losses from poor management.

Figure 1: Application efficiencies for various irrigation systems

Adapted from Robinson (2004), including data from Raine and Bakker (1996), Wood et al. (2007)


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WATER ORIGINS

Most water used for irrigation originates from Australia's major river systems, the Murray-Darling

system in eastern Australia and the Ord River in the Kimberley region of Western Australia. Othersignificant river/dam systems can be found on the Burdekin River in Queensland, in the south-west of

Western Australia and in the MacAlister district of Victoria. Another large source of water in Australia is

the ground water available from the Great Artesian Basin, which provides for livestock and crops over

much of north-eastern Australia via natural springs and man-made bores (map S16.3).

S16.3 Water consumption in Australia
http://www.abs.gov.au/ausstats/[email protected]/mf/4610.0.55.002


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TYPES OF WATER SOURCES FOR IRRIGATION

Surface water, drawn from rivers, lakes, weirs and dams, is the main source of irrigation water across all

industries. The relative importance of other water sources - groundwater (in underground streams and

aquifers), town or country reticulated mains supply, and on-farm and off-farm recycled or reused water

(used, captured, treated and reused) - varies considerably between irrigated activities and location. With

South Australia and the Northern Territory the exceptions, all other states rely mainly on surface water.

In 2004-05, irrigated farms in the Northern Territory obtained the greatest share of their water for use in

agriculture from the ground (82%) followed by South Australia (46%). New South Wales, Queensland

and Western Australia each relied on groundwater for about a quarter of their agricultural water. South

Australia was the largest absolute user of town or country reticulated mains supply as a source of water

( 47% of national use).

On-farm methods of recycling water have become popular in recent times as they can be cost effective

and resource friendly. It is generally more common on large farms (based on estimated value of

agricultural operations) and, in particular, broadacre with around 30% of all farms with broadacre crops

as their main irrigated activity, and almost all farms with cotton as their main irrigated activity,

undertaking some form of on-farm water recycling in 2002-03. However, this water may contain more

nutrients, and increase salinity, which farmers need to account for during application.

METHODS OF IRRIGATING

There are various methods of irrigation and each method offers different advantages and disadvantages

to the various crops and land types. For example, surface irrigation, which involves directing a flow of

water across the soil surface was the dominant water application method for farms producing rice

(96%), cotton (95%), and cereals other than rice (51%) in 2003-04. Drip irrigation was used on 80% of

farms where their main irrigation activity was fruit growing and 73% of farms whose main irrigation

activity was grape growing.

Soil conditions can also influence water application methods as seen on the semi-arid plains of northern

Australia and the temperate slopes and plains of southern Australia. In these locations, surface irrigation

is the preferred method for the growing of cereals (excluding rice) but in all other irrigated areas of

Australia, sprinklers were the dominant form of irrigation for cereals (excluding rice).

Developments in irrigation technology have led to the invention of sub-surface drip irrigation where drip

lines are buried 10-20 centimetres below the ground to uniformly wet the area. This method allows

water and nutrients to be applied directly to the root zone enabling the producer to manage and

optimise water use.


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Given the high losses of water incurred in agriculture (due to leaks, evaporation, etc.) and greater

recognition of the need to preserve water, these new technologies, while costly to establish, are being

increasingly used by farmers who previously used surface and sprinkler irrigation methods.

As well as irrigation methods, irrigation scheduling methods are also attracting greater attention. The

majority of farms once tended to only use their own knowledge or observation techniques but now on-

farm tools and alternative scheduling methods are also being used. Some tools used to determine when

to irrigate include; evaporation figures or graphs, tensiometers and soil probes.

IRRIGATION METHODS

Australia

Above-ground drip or trickle irrigation was the most common method of irrigation in Australia in 2008-

09, used by 11 thousand agricultural businesses. Surface irrigation was used by 7,674 agricultural

businesses and microspray sprinklers used by 5,915 agricultural businesses.

In 2008-09, the main irrigation method was surface irrigation, irrigating 804 thousand hectares. Large

mobile machines were used to irrigate 253 thousand hectares and above-ground drip or trickle irrigation

was used to irrigate 217 thousand hectares.

State/Territory

Above-ground drip or trickle irrigation was used by 23% of all agricultural businesses who irrigated in

New South Wales in 2008-09 (used by 2,337 agricultural businesses). This method was used by 52% of

irrigating agricultural businesses in South Australia (3,034) and 45% in Western Australia (1,284).

In Victoria, surface irrigation was the most common irrigation method, used by 3,600 agricultural

businesses while hose irrigation was the main method in Queensland (2,286) and Tasmania (821).

The most common method of irrigation in the Northern Territory was microspray sprinklers, used by 152

agricultural businesses.

Of all the irrigation methods used in 2008-09, surface irrigation covered the largest areas of irrigated

land in New South Wales (308 thousand hectares), Victoria (197 thousand hectares), and Queensland

(263 thousand hectares). Above-ground drip or trickle irrigation covered the largest areas of irrigated

land in South Australia (80 thousand hectares) and Western Australia (17 thousand hectares) while hose

irrigators covered the largest area of irrigated land in Tasmania (30 thousand hectares) and microspray

sprinklers covered the largest area of irrigated land in Northern Territory (3,008 hectares).


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Murray-Darling Basin

Surface irrigation was the most common method of irrigation in the Murray-Darling Basin in 2008-09,

utilised by 5,296 agricultural businesses. These businesses accounted for 69% of all agricultural

businesses in Australia using surface irrigation. Above-ground drip or trickle irrigation was the next most

common method (3,688), followed by microspray sprinklers (1,891).

The method covering the largest area of land in the Murray-Darling Basin in 2008-09 was surface

irrigation (596 thousand hectares), followed by above-ground drip or trickle irrigation (115 thousand

hectares), and large mobile machines (95 thousand hectares).

Outside the Murray-Darling Basin, above-ground drip or trickle irrigation was the most common method

of irrigation, but as for the Basin itself, surface irrigation covered the greatest area.

TOOLS USED IN IRRIGATION DECISION MAKING

The three most commonly used tools in irrigation decision-making were knowledge or observation (used

by 36 thousand agricultural businesses), soil probes (6,266), and calendar/rotational scheduling (5,604).

The main tools used in irrigation decision making in the Murray-Darling Basin in 2008-09 were the same

as for Australia as a whole: knowledge or observation (used by 14 thousand agricultural businesses), soil

probes (2,866), and calendar/rotational scheduling (2,357).

CHANGES MADE TO IRRIGATION PRACTICES

Of the 40 thousand agricultural businesses who irrigated in 2008-09, over 21 thousand (54%) reported

making one or more changes to their irrigation practices. The three most common changes made

included adopting more efficient irrigation techniques (8,770 agricultural businesses), adopting more

efficient irrigation scheduling (6,459), and reducing the area under irrigation (5,618). One of these three

changes was the most common change reported in each state/territory, with the exception of South

Australia, where the purchase of extra water was the most commonly reported change.

In the Murray-Darling Basin, of the 11 thousand agricultural businesses who reported making one or

more changes to their irrigation practices in 2008-09, the most commonly reported changes included

the adoption of more efficient irrigation techniques (38% of irrigators making one of more changes),

reducing the area under irrigation (35%), and purchasing extra water (31%).


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CHANGES INTENDED TO BE MADE TO IRRIGATION PRACTICES

Of the 20 thousand agricultural businesses in Australia that indicated they intended to make changes to

their irrigation practices after 30 June 2009, 41% indicated they would adopt more efficient irrigation

techniques, while 29% indicated they would adopt more efficient irrigation scheduling, and 27%

reported they intended increasing the area under irrigation. The most common intended change

reported in each state/territory was one of these three intended changes.

In the Murray-Darling Basin, the most common intended changes to irrigation practices included the

adoption of more efficient irrigation techniques (39%), the purchase of extra water (28%), and the

adoption of more efficient irrigation scheduling (26%).

Methods and Techniques of Irrigation

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